Leukotrienes are potent proinflammatory mediators. Our understanding of their role in allergic rhinitis has increased, but further, extensive investigation is required. The sulfidopeptide LTs are generated during the immediate response to antigen provocation and are probably increased during the late inflammatory phase and during seasonal exposure. The source of LTC4 in the early allergic reaction includes the mast cell, but other cell types may also contribute. LTD4 causes nasal congestion and increased blood flow, but not sneezing or significant rhinorrhea. Studies in which LT generation was pharmacologically reduced support a role for these mediators in allergic rhinitis. There is now a need to evaluate the more potent, recently developed, LT antagonists in rhinitis. These agents should help establish the relative importance of LTs to the many other inflammatory mediators that are implicated in the pathogenesis of allergic rhinitis. Such knowledge will broaden and improve our choice of therapeutic modalities for this disease.